1. Field of the Invention
This invention relates to an apparatus and method of protecting a tanker and/or cargo ship during breach of the hull. More particularly, this invention relates to a novel apparatus and method for protecting the tanker and preventing spillage of its contents from occurring during such a breach by means of sealing any ruptures in the hull with a foamable cast-cure plastic material.
2. Discussion of Related Art
Transportation of petroleum products, such as crude oil, on the open seas poses a risk to the environment as well as the potential for economic loss in the case of a breach of the hull of the vehicle with resulting spillage of the vehicle's cargo. One example of such an event is the Exxon Valdez oil spill in Alaska's Prince William Sound which occurred in March 1989. In 1990 the U.S. Government enacted the Oil Pollution Act of 1990 setting forth a more stringent set of requirements for construction of oil tankers and more specifically the design of the hull of such vehicles. This new law requires that all U.S. oil tankers be fitted with a double hull construction. Accordingly, the Oil Pollution Act of 1990 seeks to minimize the risk to tanker type vehicles of spillage to the vessel's contents resulting from a collision or grounding of the vehicle.
In a vessel containing a double hull construction, the outer walls of the vessel are effectively duplicated by means of a second set of rigid interior walls. The two sets of walls enclose an empty space which is generally filled with a non-flammable gas at such time as the vessel is in a standard operating mode.
There are several drawbacks associated with a double hull construction of a vessel such as an oil tanker. First, double hulled vessels are expensive to manufacture as well as to operate. In actuality they require building an entire second hull which must be constructed so as to withstand enormous loads. Construction in the form of retrofitting additional hulls inside vessels which are in service is very difficult, as well as expensive. Furthermore, due to the double hull structure, it is difficult to inspect and/or perform repairs within spaces between an outer hull and an inner hull in the event such action becomes necessary. Accordingly, there appears to be a need for an alternative to the conventional double hull construction for storage vessels which can provide added safety to the environment while avoiding the drawbacks and dangers associated with conventional double hull vessels.
In view of the prior art disclosed, there have been numerous proposals for avoiding the need for double hull construction of a storage vessel. For example, U.S. Pat. No. 1,320,012 to Lee et al. discloses a solution to salvaging a ruptured vessel compartment. The patent discloses the use of inflatable bags for deployment into a compartment which has been breached. The bags are filled with a gas until such time as the gas pressure inside the bags is equal to the pressure of the surrounding water. However, the Lee et al. patent fails to address the issues pertaining to the structural integrity of the inflatable bags against the forces acting across a large hull breach. Accordingly, the gas inflated bags may provide sufficient strength for a smaller size vehicle as well as a minor breach, however, when applying this apparatus to a tanker vessel, such a mitigating apparatus may not be sufficient to withstand the forces associated with a significant breach of the hull.
Furthermore, U.S. Pat. No. 2,966,131 to Elijah discloses the use of gas filled bags for sealing off a hatch opening in the event of a breach, as well as displacing water from the area where the breach has occurred. However, the disclosure does not appear to account for significant pressure applied to a vessel hull in the event of a breach. Although such a disclosure may be sufficient to withstand a breach of the hull in a smaller size vessel, the mechanics of the structure cannot be retrofitted to a storage vessel such as a conventional oil tanker or supertanker. The force of the water bearing against the hull in the event of a breach is enormous, and the sheets and pillows disclosed in the Elijah patent do not have the strength to withstand the pressure associated with such a breach. Accordingly, such a disclosure does not provide a means for sealing the breach and holding the seal for an extended period of time until such rupture may be cured.
U.S. Pat. No. 5,125,439 to Perkins discloses a construction similar to a double hull construction, wherein foam prevents evaporation of vapors. However, the Perkins patent does not teach a liquid polymer for sealing the compartment in the event of a breach, nor does it disclose a foam comprising strength and buoyancy to seal the breach without compromising the integrity of the hull as aqueous foam does not provide such properties. Accordingly, the Perkins patent neither provides the structure nor the materials for sealing a compartment of the hull of a vehicle which has been ruptured.
In view of all of the disclosures which provide means for filling hull compartments with gas inflated bags or foam material for preventing evaporation of vapors, none provide a compact apparatus for directing a foamable cast-cure plastic material to the site of the hull breach, wherein such polymer seals the breach and comprises sufficient strength to withstand the pressure of the external water applied to the area of the breach. Accordingly, there remains a need for a feasible and effective alternative to the conventional double hull construction which can be retrofitted to existing vessel so as to overcome the obstacles associated with conventional double hull construction.
Therefore, what is desirable is an apparatus and method for providing the protection of a conventional double hull to both existing and new tanker constructions at a relatively inexpensive cost. The novel double hull construction incorporating the spillage protection system provides a superior level of protection against cargo loss while providing a compact apparatus for delivering a material to the area of breach without compromising the structure or cargo capacity of the vessel.